Conductive articles and intermediates containing heavy pnictide mixed alkaline earth oxide layers

Abstract

Articles are disclosed in which an electrically conductive layer on a substrate exhibits a superconducting transistion temperature in excess of 90° K. Conductive layers are disclosed comprised of a crystalline heavy pnictide mixed alkaline earth copper oxide. Processes of preparing these articles are disclosed in which a mixed oxide precursor composition is coated and heated to its thermal decomposition temperature to create an amorphous mixed metal oxide layer. The amorphous layer is then heated to its crystallization temperature.

What is claimed is: 
     
       1. An article comprised of an alkaline earth oxide substrate and an electrically conductive layer located on the substrate characterized in that the electrically conductive layer is comprised of a crystalline heavy pnictide mixed alkaline earth copper oxide satisfying the formula (II)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2 O.sub.y                (II)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium;   x is from 0.5 to 1.5; and   y is the amount of oxygen that results from heating an amorphous mixture of oxides of P, A, Ca and Cu satisfying the ratio   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     in the form of a coating having a thickness of 1 μm or less on the substrate to a temperature in the range of from 780° to 1000° C. in the presence of air.     
     
     
       2. An article comprised of substrate and an electrically conductive layer located on the substrate characterized in that the substrate exhibits a perovskite crystal structure and the electrically conductive layer is comprised of a crystalline heavy pnictide mixed alkaline earth copper oxide satisfying the formula (II)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2 O.sub.y                (II)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium;   x is from 0.5 to 1.5; and   y is the amount of oxygen that results from heating an amorphous mixture of oxides of P, A, Ca and Cu satisfying the ratio   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     in the form of a coating having a thickness of 1 μm or less on the substrate to a temperature in the range of from 780° to 1000° C. in the presence of air.     
     
     
       3. An article comprised of a substrate, a barrier and an electrically conductive layer located on the barrier characterized in that the substrate is chosen from the group consisting of alumina, silica and silicon, the barrier is comprised of hafnia or zirconia and the electrically conductive layer is comprised of a crystalline heavy pnictide mixed alkaline earth copper oxide satisfying the formula (II)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2 O.sub.y                (II)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium;   x is from 0.5 to 1.5; and   y is the amount of oxygen that results from heating an amorphous mixture of oxides of P, A, Ca and Cu satisfying the ratio   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     in the form of a coating having a thickness of 1 μm or less on the substrate to a temperature in the range of from 780° to 1000° C. in the presence of air.     
     
     
       4. An article comprised of a substrate and an electrically conductive layer located on the substrate characterized in that the substrate is silver and the electrically conductive layer is comprised of a crystalline heavy pnictide mixed alkaline earth copper oxide satisfying the formula (II)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2 O.sub.y                (II)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represent strontium or strontium in combination with a minor amount of barium;   x is from 0.5 to 1.5; and   y is the amount of oxygen that results from heating an amorphous mixture of oxides of P, A, Ca and Cu satisfying the ratio   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     in the form of a coating having a thickness of 1 μm or less on the substrate to a temperature in the range of from 780° to 1000° C. in the presence of air.     
     
     
       5. An article comprised of a substrate and a layer of an amorphous metal oxide located on the substrate characterized in that the substrate exhibits a perovskite crystal structure and the amorphous metal oxide is a heavy pnictide mixed alkaline earth copper oxide exhibiting (a) a ratio of metal (I)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium; and   x is from 0.5 to 1.5; and     (b) an oxygen content which results from (i) forming a solution comprised of a volatilizable film-forming solvent and metal-carboxylate ligand compounds of the metals and in the proportions of (I), (ii) coating the solution on the substrate, and (iii) removing the solvent and ligands from the substrate by heating in the presence of air.   
     
     
       6. An article comprised of a substrate, a barrier layer and a layer of an amorphous metal oxide located on the barrier characterized in that the barrier layer is comprised of hafnia or zirconia, the substrate is chosen from the group consisting of alumina, silica and silicon, and the amorphous metal oxide is a heavy pnictide mixed alkaline earth copper oxide exhibiting (a) a ratio of metal (I)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     wherein   P is bismuth or bismuth in combination with antimony is a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium; and   x is from 0.5 to 1.5; and     (b) an oxygen content which results from (i) forming a solution comprised of a volatilizable film-forming solvent and metal-carboxylate ligand compounds of the metals and in the proportions of (I), (ii) coating the solution on the substrate, and (iii) removing the solvent and ligands from the substrate by heating in the presence of air.   
     
     
       7. An article comprised of a substrate and a layer of an amorphous metal oxide located on the substrate characterized in that the substrate is silver and the amorphous metal oxide is a heavy pnictide mixed alkaline earth copper oxide exhibiting (a) a ratio of metal (I)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium; and   x is from 0.5 to 1.5; and     (b) an oxygen content which results from (i) forming a solution comprised of a volatilizable film-forming solvent and metal-carboxylate ligand compounds of the metals and in the proportions of (I), (ii) coating the solution on the substrate, and (iii) removing the solvent and ligands from the substrate by heating in the presence of air.   
     
     
       8. An article according to claim 1, 2, 3 or 4 further characterized in that the conductive layer is restricted to a portion of the substrate thereby defining a conduction path on the substrate. 
     
     
       9. An article according to claim 4 further characterized in that both the substrate and the conductive layer are flexible. 
     
     
       10. An article according to claim 1, 2, 3, or 4 further characterized in that the conductive layer has a thickness of 5 μm or less. 
     
     
       11. An article according to claim 1 further characterized in that the substrate is magnesia. 
     
     
       12. An article according to claim 2 further characterized in that the substrate is strontium titanate. 
     
     
       13. An article according to claim 1, 2 or 3 further characterized in the substrate is monocrystalline. 
     
     
       14. An article according to claim 1, 2, 3 or 4 further characterized in that the crystalline heavy pnictide mixed alkaline earth copper oxide is oriented with its longest crystal axis substantially perpendicular to the substrate. 
     
     
       15. An electrically conductive article according to claim 1, 2, 3 or 4 further characterized in that the conductive layer exhibits a superconducting transition temperature of greater than 90° K. 
     
     
       16. An article according to claim 15 further characterized in that the conductive layer exhibits superconductivity at a temperature greater than 77° K. 
     
     
       17. An article according to claim 1, 2, 3 or 4 further characterized in that the conductive layer consists of greater than 30 percent by volume of a crystalline oxide conductive phase satisfying the metal ratio   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2     where   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based upon bismuth,   A consists essentially of strontium or strontium in combination with barium, and   x is 0.5 to 1.5.   
     
     
       18. An article according to claim 16 further characterized in that said conductive layer consists of greater than 70 percent by volume of said crystalline oxide conductive phase. 
     
     
       19. An article according to claim 16 further characterized in that said conductive layer consists of greater than 90 percent by volume of said crystalline oxide conductive phase. 
     
     
       20. An article according to claim 16 further characterized in that P consists essentially of bismuth. 
     
     
       21. An article comprised of a substrate and a layer of an amorphous metal oxide located on the substrate characterized in that the substrate is an alkaline earth oxide and the amorphous metal oxide is a heavy pnictide mixed alkaline earth copper oxide exhibiting (a) a ratio of metals (I)   P.sub.2 A.sub.3-x Ca.sub.x Cu.sub.2                        (I)     wherein   P is bismuth or bismuth in combination with antimony in a concentration of less than 10 mole percent based on bismuth;   A represents strontium or strontium in combination with a minor amount of barium; and   x is from 0.5 to 1.5; and     (b) an oxygen content which results from (i) forming a solution comprised of a volatilizable film-forming solvent and metal-carboxylate ligand compounds of the metals and in the proportions of (I), (ii) coating the solution on the substrate, and (iii) removing the solvent and ligands from the substrate by heating in the presence of air.   
     
     
       22. An article according to claim 21, 5, 6 or 7 further characterized in that the substrate presents a planar surface and the amorphous metal oxide forms a planar layer on the planar substrate surface. 
     
     
       23. An article according to claim 1, 2, 3, 4, 21, 5, 6 or 7 further characterized in that the electrically conductive layer includes from 0.2 to <10 mole percent antimony with respect to the bismuth. 
     
     
       24. An article according to claim 23 further characterized in that the electrically conductive layer includes from 0.5 to <5 mole percent antimony with respect to bismuth. 
     
     
       25. An article according to claim 3 or 6 further characterized in that the barrier layer comprises zirconia. 
     
     
       26. An article according to claim 25 further characterized in that said substrate is selected from the group consisting of fused quartz, single crystal silicon, single crystal silicon having an SiO 2  film over the surface thereof, sapphire and polycrystalline alumina. 
     
     
       27. An article according to claim 3 or 6 further characterized in that said substrate is silicon and said barrier layer is a barrier layer triad comprised of a first triad layer located adjacent the silicon substrate consisting essentially of silica, a third triad layer remove from the silicon substrate consisting essentially of one Group 4 heavy metal oxide, and a second triad layer interposed between the first and third triad layers comprising a mixture of silica and at least one Group 4 heavy metal oxide. 
     
     
       28. An article according to claim 27 further characterized in that the second and third triad layers each have a thickness in the range of from 1000 to 5000 Å.